Use const in C to protect the notes of array content

For example: int sum (const int ar [], int n)

If const int days [MONTHS] = {31, 28, 31}, the array content cannot be changed.

If:

Double rates [5] = {88.9, 100.12, 59.45, 183.11, 340.5 };
Const double * pd = rates;

You cannot use the pc to modify the value it points to. However, you can still modify the value through rates [0] because rates is not a constant.

If we change the writing method to double * const pc = rates, we can modify the data but cannot move the pointer.

If the above two are used in combination, it is equivalent to the use of strong glue, how can not be moved:

Const double * const pc = rates.